FIGS. 9 through 13 show a light-reflecting rotary encoder of the prior art. FIG. 9 is a sectional side view, FIG. 10 is a plan view of a base member which is the principal portion of the rotary encoder in FIG. 9, FIG. 11 is a perspective view of a detent spring of the same, FIG. 12 is a perspective view of a pulse plate of the same, and FIG. 13 is a diagram showing the operation of the same.
In FIGS. 9 through 12, reference numeral 1 denotes a base member made from die cast zinc or other material. A cylindrical support shaft 2 extends perpendicularly up from the center of the disc-shaped bottom surface of the base member, and a circular detent member 3 having protrusions formed continuously in the radial direction at a fixed angular pitch is provided at a fixed radius from the center of the base member.
An operating shaft 4 is rotatably supported on the support shaft 2, and in the vicinity of the lower end thereof, there disposed a detent spring 5 made from a flexible sheet metal and having a flexible contact protrusion 5' for engaging the circular detent member 3 so as to give a clicking detent sensation, and a pulse plate 8 on which glossy light-reflective portions 6 and non-reflective slits 7 are alternately and continuously provided, the number of the glossy light-reflective portions 6 being the same as that of the protrusions on the circular detent member 3. The reference numeral 15 denotes a retainer washer for holding the operating shaft 4 in place.
An optical element 13 of reflective detector type in which a light-emitting element 11 and light-receiving element 12 are arranged side by side is fixed to and has continuity with a conductor plate 10 which is formed inside an insulating substrate 9 fixed on the top surface of the base member 1, so that the optical element 13 opposes the light-reflective portions 6 and slits 7 of the above-mentioned pulse plate 8, the optical element 13 and pulse plate 8 attached to the above-mentioned operating shaft 4 generating pulse signals. The operation of this conventional light-reflecting rotary encoder is described below with reference to FIG. 13.
In the drawing, when the pulse plate 8 is rotated right or left by rotating the operating shaft 4, the light-reflective portions 6 and non-reflective slits 7 alternately face the optical element 13 in agreement with the clicking detent sensation. When the light emitted from the light-emitting element 11 is reflected at the reflective portions 6 of the pulse plate 8, the light-receiving element 12 receives the reflected light and outputs a high level signal to a terminal 14. On the contrary, when the light from the light-emitting element 11 passes through the non-reflective slits 7, a low level signal is output.
Therefore, pulse signals corresponding to the rate of rotation of the operating shaft 4 can be output to the terminal 14 in agreement with the clicking detent sensation.
Furthermore, by providing two optical elements 13 of such a reflective detector type, pulse signals with shifted phases can be output from the optical elements corresponding to the direction of rotation, respectively.
In the above-mentioned light-reflecting rotary encoder, the timing of the clicking detent sensation needs to perfectly match the timing with which the pulse signals are generated in agreement with the clicking detent sensation. In the rotary encoder with the above-mentioned configuration, however, the clicking detent sensation corresponding to the angle of rotation of the rotating shaft 4 is generated by the detent spring 5 at the end of the shaft and the circular detent member 3 on the bottom surface of the base member, while the pulse signals being generated between the pulse plate 8 at the end of the shaft and the optical element 13 attached to the insulating substrate 9. Therefore, since the clicking detent sensation and the pulse signals are respectively generated by assemblies of different components, it has been difficult to adjust the timing of the two due to differences in the precision of components, shifts in assembling the components or the like, and it has been particularly difficult when there were a large number of pulses per rotation.
Also, after long periods of use or after being bumped, a shift is caused between the detent spring 5 and the pulse plate 8.
Moreover, the flexible contact protrusion 5' which is disposed between the detent spring 5 and the circular detent member 3 and generates the clicking detent sensation becomes worn due to friction during rotation, so it has been difficult to guarantee a useful life of greater than 100,000 rotations.